opDispatch shadowing toString - feature or bug?

[Damian Ziemba]

On Thu, 01 Sep 2011 13:59:29 +0200, Timon Gehr wrote:

> static assert(isInputRange!Test);
> static assert(isInputRange!Test2);
> 
> toString is not shadowed, but the implementation of writeln assumes that
> your types are an InputRange (they provide, by the means of opDispatch,
> front(), empty() and popFront())
> 
> The fact that writeln([]); prints a new line instead of "[]" is a bug
> that has already been taken care of in a pull request afaik.
> 
> This specific problem can be solved by making your types not follow the
> InputRange interface, by putting an appropriate constraint on your
> opDispatch.
> 
> 
> import std.stdio;
> 
> struct Test
> {
> 	string opDispatch( string key )() if(key!="popFront") {
> 		return "I am dispatching in struct!";
> 	}
> 
> 	string toString()
> 	{
> 		return "I am Test struct!";
> 	}
> }
> 
> class Test2
> {
> 	string opDispatch( string key )() if(key!="popFront") {
> 		return "I am dispatching in class!";
> 	}
> 
> 	string toString()
> 	{
> 		return "I am Test class!";
> 	}
> }
> 
> void main()
> {
> 	Test test = Test();
> 	writeln ( test.s ); // I am dispatching in struct! writeln 
( test.s()
> 	); // I am dispatching in struct! writeln ( test ); //I am Test 
struct!
> 	
> 	Test2 test2 = new Test2();
> 	writeln ( test2.s ); // I am dispatching in class! writeln 
( test2.s()
> 	); // I am dispatching in class! writeln ( test2 ); // I am Test 
class!
> }

Yes, this fix the problem.

Hmm, after all its a bit loose of a keyword, becouse I can't use anymore
test.popFront. For example if class acts as a storage device 

class Storage
{
	string[ string ] vars;

	string opDispatch( string key )() if ( key != "popFront" )
	{
		if ( key in vars ) return vars[ key ];
		else return "";
	}

	string toString() { // implement me
	}
}

auto storage = new Storage;
storage.vars["test"] = "I'm a test!";
storage.vars["popFront"] = "I'm a poping around! :D";

writeln( storage.test ); // I'm a test! 
writeln( storage.popFront ); // error

Ofcours, in opDispatch I can use empty or front instead of popFront but 
it is still loose of one keyword.

Looks like it's a loose I have to take :-)

Thank you very much for reply!

Best regards,
Damian Ziemba